Electrospun O-quaternary ammonium chitosan/polyvinyl alcohol nanofibrous film by application of Box-Behnken design response surface method for eliminating pathogenic bacteria.

In this study, O-quaternary ammonium chitosan (O-HTCC) containing bicationic antibacterial active groups was synthesized to develop an O-HTCC/PVA porous nanofibrous film to enhance antibacterial activity, leveraging surface modification and nano-porous structure design. Uniform and smooth nanofibrous structures (average diameter: 72-294 nm) were successfully obtained using a simple and feasible electrospinning method. A response surface model via Box-Behnken design (BBD) was used to clarify the interaction relationship between O-HTCC fiber diameter and three critical electrospinning parameters (O-HTCC concentration, applied voltage, feed flow rate), predicting that the minimum O-HTCC fiber diameter (174 nm) could be achieved with 7 wt% of O-HTCC concentration, 14 kV of voltage, and 0.11 mL/h of feed flow rate. Linear regression (R2 = 0.9736, Radj2 = 0.9716) and the Anderson Darling test demonstrated the excellent fit of the RSM-BBD model. Compared to N-HTCC/PVA nanofibrous film, the O-HTCC/PVA version showed increased growth inhibition and more effective antibacterial efficacies against Escherichia coli (E. coli) (~86.34 %) and Staphylococcus aureus (S. aureus) (~99.99 %). DSC revealed improved thermal stability with an increased melting temperature (238 °C) and endothermic enthalpy (157.7 J/g). This study holds potential for further development of antibacterial packaging to extend food shelf-life to reduce bacterial infection.

PLGA Cage-Like Structures Loaded with Sr/Mg-Doped Hydroxyapatite for Repairing Osteoporotic Bone Defects.

Poly(lactic-co-glycolic acid) (PLGA)-based porous structures have a widespread application in bone defects. To solve its flaws in the bone application, hydroxyapatite (HA) is often introduced into PLGA-based systems, and ion doping endows HA with more biological activity. In osteoporotic bone defects, the decreased activity of osteoblasts and the hyperactive osteoclasts results in slow bone repair. Strontium (Sr) can promote bone regeneration and inhibit bone resorption and has been used in the treatment of osteoporosis. Magnesium (Mg) cannot only enhance the regeneration of bone tissue but also vessels. In this study,the aim is to fabricate a multifunctional porous structure that can promote osteogenesis, and angiogenesis and inhibit osteoclasts for repairing osteoporotic bone defects. PLGA cage-like structures loaded with Sr- and Mg-doped HA (Sr/Mg@HA/PLGA-CAS) are prepared; they have large pores, suitable hydrophilicity, and can continuously release Mg2+ and Sr2+ , which facilitate cell adhesion and growth. The results show that Sr/Mg@HA/PLGA-CAS can motivate the osteogenic activity of osteoblast precursor cells and angiogenic ability of endothelial cells, and suppress osteoclast differentiation in vitro. This study indicates that Sr/Mg@HA/PLGA-CAS can assist osteogenesis, and angiogenesis while restraining osteoclast differentiation, which may have a potential application value in osteoporotic bone defects.

Preparation of multigradient hydroxyapatite scaffolds and evaluation of their osteoinduction properties.

Porous hydroxyapatite (HA) scaffolds are often used as bone repair materials, owing to their good biocompatibility, osteoconductivity and low cost. Vascularization and osteoinductivity of porous HA scaffolds were limited in clinical application, and these disadvantages were need to be improved urgently. We used water-in-oil gelation and pore former methods to prepare HA spheres and a porous cylindrical HA container, respectively. The prepared HA spheres were filled in container to assemble into composite scaffold. By adjusting the solid content of the slurry (solid mixture of chitin sol and HA powder) and the sintering temperature, the porosity and crystallinity of the HA spheres could be significantly improved; and mineralization of the HA spheres significantly improved the biological activity of the composite scaffold. The multigradient (porosity, crystallinity and mineralization) scaffold (HA-700) filled with the mineralized HA spheres exhibited a lower compressive strength; however, in vivo results showed that their vascularization ability were higher than those of other groups, and their osteogenic Gini index (Go: an index of bone mass, and inversely proportional to bone mass) showed a continuous decrease with the implantation time. This study provides a new method to improve porous HA scaffolds and meet the demands of bone tissue engineering applications.

Mesophilic anaerobic co-digestion of residual sludge with different lignocellulosic wastes in the batch digester.

Co-digestion of residual sludge (RS) and different lignocellulosic wastes (LWs) including greening waste (GW), decocted Chinese herbs waste (DCHW) and sugarcane bagasse waste (SCBW) was investigated in batch digester. Results show that the application of GW presented the highest specific methane yield (161 mL CH4/g VSadded) due to its high carbohydrate fraction and more balanced C/N ratio in co-substrate mixture. Buswell equation was applied and it is found that biodegradability index (BI) for co-digestion varied from 68.1% to 74.2% (53.0% for RS mono-digestion) depending on the lignin fractions of the LWs. Variation of pH, VFAs, alkalinity and ammonia throughout the digestion were also examined. The addition of LWs induced VFAs formation, as well as their conversion to methane. The higher microbial diversity in RS/LWs co-digestion further confirmed the positive effect of LWs addition in co-digestion.